The downsizing of semiconductor devices continues with precise doping and ultra-shallow junctions required for the containment of short-channel effects, improvement of parasitic resistance, and the like. Various advanced methods to obtain shallow junctions having low resistance have been developed. Recently, laser annealing (LA) methods have received considerable interest as one of the alternatives for the formation of the ultra-shallow junctions. The laser annealing process has several advantages over other conventional annealing methods: (1) An extremely low thermal budget introduced within a short time period for minimizing dopant diffusion, typically less than a millisecond; (2) selective annealing and re-crystallizing of specific regions of the device and to specific depths within the device; (3) high dopant activating results since higher annealing temperature can be achieved. High dopant activation is a result of the increased dopant solid solubility in silicon. However, current laser annealing processing poses some problems in semiconductor device manufacturing. One problem encountered in the fabrication of a silicon workpiece is warping of the substrate surface and generation of slips of silicon crystal lattice during the laser annealing process. This warping often shows up as alignment problems at subsequent patterning steps and therefore reduces process yield. It is common for a wafer to become warped and slip defects are generated during ultra-high temperature (e.g., greater than 1200 degrees Celsius), laser anneal processes, especially when the annealing temperature is close to the melting point of the wafer (e.g. 1410 degrees Celsius for silicon wafers). During the anneal, the residual stress and visoplastic strain could be induced due to the low yield strength and the high thermal stress induced by nonuniform temperature distribution and thermal expansion mismatch among dissimilar materials. This is likely the cause of the bending (warpage) and plastic deformation (slip) in the integrated structures. Another difficulty encountered in a laser annealing process is breaking of the workpiece. This is frequently and most noticeably encountered at the edge of the workpiece if a laser beam of full process power hits at the workpiece edge, wherein a portion of the edge can break off.
Accordingly, there is a need for improved laser annealing processing by which the benefits of laser annealing can be achieved while avoiding or mitigating the problems encountered in the conventional laser annealing techniques.